The present invention relates to ophthalmic lenses made from polymeric compositions. More particularly, the invention relates to ophthalmic lenses, preferably deformable intraocular lenses, having reduced surface tackiness made from acrylate and/or methacrylate-based polymeric compositions.
Intraocular lenses (IOLs) have been known for a long time, since shortly after the end of World War II. Such a lens is surgically implanted into a mammalian eye, e.g., human eye, to replace a damaged or diseased natural lens of the eye and restore the patient's vision.
Although IOLs are made from "hard" or "rigid" polymeric or glass optical materials, such as polymethyl methacrylate (which has a refractive index of 1.49), soft resilient polymeric materials, such as silicones, have been increasingly used, for the reasons discussed below, in ophthalmic applications.
Since soft IOLs are deformable, for example, foldable or rollable, for implantation, a smaller incision can be surgically cut in the eye than for the implantation of "hard" IOLs of the same optical power. The smaller the incision, the less trauma the patient's eye experiences and the faster post-operative healing occurs. An incision of about 3 mm is ideal since this size incision is presently required to remove the natural lens after it has been broken up, for example, emulsified in a conventional phaceoemulsification procedure. In contrast the typical IOL optic has a diameter of about 6 mm.
The size and mechanical characteristics of the deformable IOLs play an important role. As is well understood by those skilled in the art, for successful implantation, the deformable IOL must have sufficient structural integrity, elasticity and elongation and be small enough in size to permit deforming for insertion through a small incision. After insertion, the lens must, of course, regain its original shape and have sufficient structural integrity to retain such shape under normal use conditions.
In general, the thinner the deformable IOL the smaller the incision in the eye that is required. On the other hand, in order to function optically as an IOL, the lens must have sufficient optical refractory power. Also, the higher the optical refractive index of the material making up the IOL, the thinner the IOL can be and still obtain the same optical refractory power.
Deformable IOLs made of acrylic materials can be quite tacky in nature, which tackiness inhibits deforming to a sufficiently small size for insertion through a very small incision and/or may cause handling problems Gupta U.S. Pat. No. 4,834,750 discloses IOLs with optics made of copolymers of methacrylate esters which form homopolymers that are relatively hard at room temperature and acrylate esters which form homopolymers that are relatively soft at room temperature. Such copolymers are cross-linked with a diacrylate ester to produce an acrylate material which preferably includes a constituent derived from a fluoroacrylate to reduce surface tackiness. None of the specific monomers disclosed in this patent provide homopolymers which have a refractive index of at least about 1.50.
Weinschenk, III U.S. Pat. No. 5,331,073 discloses acrylic-based intraocular lenses which optionally include a constituent derived from a hydrophilic monomeric component. This constituent is effective to reduce the tackiness of the copolymer. However, such hydrophilic constituent may cause a disadvantageous decrease in the index of refraction of the final IOL optic in that some water is included within the copolymer.
LeBoeuf et al U.S. Pat. No. 5,603,774 discloses plasma treatment of the polymer surface to reduce tackiness associated with certain acrylic polymers, particularly those polymers useful in intraocular lenses. However, such plasma treatment does involve an additional manufacturing step. Also, the non-homogeneous intraocular lens which results from the surface being treated with plasma has the potential of causing problems in the eye.
It would be advantageous to provide ophthalmic lens materials of construction which have good optical properties, including optical clarity and high refractive index (index of refraction) and, in addition, have reduced tackiness without the disadvantages of the prior art materials noted above.